TAMPA — In the beginning of camp, Eduardo Nunez was reticent about the changes Mick Kelleher was attempting to make with his throwing motion.

Kelleher, a former big league infielder and current Yankees first base coach, decided before camp opened a change to the error-prone Nunez’s throwing motion had to be made.

“In my opinion and Joe [Girardi’s] opinion, something had to change,’’ Kelleher said. “To play shortstop you have to be an accurate thrower. It wasn’t about catching the ball, it wasn’t that.’’

Some voices believed Nunez belonged in the outfield. Others suggested Nunez become a full-time designated hitter at 25. General manager Brian Cashman didn’t think Nunez’s bat was strong enough to play a corner outfield spot. So the Yankees’ party line was Nunez was a shortstop despite committing 18 of his big league errors as a shortstop.

So, Kelleher was entrusted with making Nunez’s above-average arm — in terms of strength — more accurate.

“Before my arm action was long, never short,’’ said Nunez, who made seven errors at three positions last season, four of those on throws. “All my life it was long. Now it’s short and it feels good so far.’’

“It was uncomfortable,’’ said Nunez, who used to catch the ball and swing his arm around the back of his body before releasing it. “Now, it’s much better. I have worked on it since the first day of camp. The first few days of camp it was really bad. Now it feels better. I have made the adjustment.’’

Kelleher got Nunez to catch the ball and bring his arm to shoulder level before releasing. His belief was Nunez wouldn’t suffer a decrease in arm strength while trying to be more accurate.

“We worked on it every day since he got here,’’ Kelleher said. “We wanted him to throw like [Derek] Jeter throws, like Robbie [Cano] throws. We wanted him to shorten it up.’’

As a roving infield instructor for the Yankees from 2006-08 Kelleher worked with Nunez on shortening the arm action, but when Kelleher was added to Girardi’s staff in 2009, Nunez went back to throwing the long way.

When Kelleher implemented the shorter action, Nunez pushed back a bit.

“He said he was uncomfortable,’’ Kelleher said. “I said, ‘Well, did you expect anything else?’ ’’

Part of Nunez’s long motion was his long limbs.

“He has long arms that are real loose,’’ Kelleher said. “There is a lot of movement going on.’’

Nunez made seven errors in 38 games a year ago and after two errors (one throwing; one fielding) as a third baseman on May 10, Nunez was banished to Triple-A Scranton Wilkes-Barre. When the rosters expanded on Sept. 1, Nunez was recalled.

Two throwing errors as a shortstop that fueled a 5-4 loss to the A’s on Sept. 23 resulted in one more start for Nunez the rest of the regular season. He did start Game 3 of the ALCS against the Tigers at short and Game 4 at third without incident.

Because Jeter isn’t likely to play exclusively at short when the season starts, it’s possible Nunez could be his replacement.

However, Nunez isn’t a lock for a roster spot because, by carrying Travis Haffner, who is strictly a DH, the Yankees will have to chose between Jayson Nix, who can play second, short and third, and Nunez, who they view only as a shortstop.

His bat is legitimate and Nunez’s speed would be a welcome addition. But it might be Kelleher shortening his arm action that makes the difference.

Yankees Training Day

Going, going ‘Ron’

He has no chance to make the team because he really doesn’t have a position, but Ronnier Mustelier’s rep as a hitter coming into camp has held up. He homered yesterday and is 3-for-6 (.500) in four games.

Today’s Schedule

Ivan Nova makes his spring debut against the Red Sox in Fort Myers, Fla. Nova is competing against David Phelps for the fifth spot in the rotation. Phelps has thrown five scoreless innings in two games.

Trial and error

Yankees committed four errors yesterday and have 13 in eight games.

Caught my eye

Empty seats. Attendance was announced at 9,498 but there were a lot less at GMS Field. Thursday’s gate was announced at 7,964 but that wasn’t close. GMS holds 11,076.